General Information
sar is used for displaying collected activity counters of various OS stats, including CPU, memory, swap, and disk I/O.
Checklist
1) Install sysstat (Red Hat or Debian)
yum install sysstat or apt-get install sysstat
2) Enable collection
vim /etc/default/sysstat
Change (Enabled=“false”) to (Enabled=“true”).
3) Modify Collection Interval (optional)
vim /etc/cron.d/sysstat
Look for a line like this to edit:
# Activity reports every 10 minutes everyday 5-55/10 * * * * root command -v debian-sa1 > /dev/null && debian-sa1 1 1
4) Start the service
service sysstat start
5) Enable on boot (Red Hat or Debian)
chkconfig sysstat on or update-rc.d sysstat defaults
After sysstat has collected data for a while, you can start to view the information with sar.
Sar logs to either:
With each log file named after the day of the month it is.
Best by visual example:
ls -l /var/log/sysstat/ -rw-r--r-- 1 root root 116880 Dec 1 22:35 sa01 -rw-r--r-- 1 root root 105984 Dec 2 22:05 sa02 -rw-r--r-- 1 root root 66032 Dec 3 20:15 sa03
These files can be read by sar using the “-f <path-to-file” flag.
sar -u (displays for current day until that point) sar -u 1 5 (display real time CPU every 1 second, 5 times) sar -u -f /var/log/sysstat/sa01 (display CPU usage on the 1st day of the month)
Linux 3.13.0-39-generic (dt-bill) 12/03/2014 _x86_64_ (4 CPU) 05:22:31 PM LINUX RESTART 05:25:01 PM CPU %user %nice %system %iowait %steal %idle 05:35:01 PM all 3.70 0.09 0.50 0.56 0.00 95.15 05:45:01 PM all 4.26 0.25 0.62 0.23 0.00 94.64
Columns:
sar -r (display todays memory stats) sar -r 2 10 (display real time memory stats every 2 seconds, 10 times)
sar -r Linux 3.13.0-39-generic (dt-bill) 12/03/2014 _x86_64_ (4 CPU) 05:25:01 PM kbmemfree kbmemused %memused kbbuffers kbcached kbcommit %commit kbactive kbinact kbdirty 05:35:01 PM 6514076 1661656 20.32 94056 657736 2300940 13.89 1008760 455492 580
Columns (probably the only ones you care about):
sar -S (todays swap usage)
sar -S Linux 3.13.0-39-generic (dt-bill) 12/03/2014 _x86_64_ (4 CPU) 05:25:01 PM kbswpfree kbswpused %swpused kbswpcad %swpcad 05:35:01 PM 8388604 0 0.00 0 0.00
Columns:
sar -b (todays disk I/O and transfer rates)
sar -b Linux 3.13.0-39-generic (dt-bill) 12/03/2014 _x86_64_ (4 CPU) 05:25:01 PM tps rtps wtps bread/s bwrtn/s 05:35:01 PM 26.47 23.27 3.20 765.51 464.86
Columns:
sar -n TYPE (todays network statistics)
TYPE can be:
Example (device stats for just eth1 from 5pm to 6pm today)
sar -n DEV -s 17:00:00 -e 18:00:00 | grep eth1 05:25:01 PM IFACE rxpck/s txpck/s rxkB/s txkB/s rxcmp/s txcmp/s rxmcst/s %ifutil 05:35:01 PM eth1 13.77 11.45 12.31 1.37 0.00 0.00 0.05 0.01 05:45:01 PM eth1 23.35 17.53 27.06 2.09 0.00 0.00 0.04 0.02 05:55:01 PM eth1 50.00 35.92 63.80 3.92 0.00 0.00 0.04 0.05 Average: eth1 29.04 21.64 34.39 2.46 0.00 0.00 0.04 0.03
Report only specfic time periods
CPU stats for today, from 6pm to 6:30pm
sar -u -s 18:00:00 -e 18:30:00
Memory stats 1pm to 3pm, from the 1st day of the month
sar -r -s 13:00:00 -e 15:00:00 -f /var/log/sysstat/sa01